Method of converting modes of wave motion for transmission from rectangular to circular wave guides



Feb. 25, 1958 F. E. PARIS! 2,325,031

. METHOD OF CONVERTING MODES 0F WAVE MOTION FOR TRANSMISSION FROM RECTANGULAR T0 CIRCULAR WAVE GUIDES Filed Dec. 15, 1951 3 Sheets-Sheet 1 IN V EN TOR.

FRANK E. PARVISI 7 W Feb. 25, 1958 PARIS} 2,825,031

METHOD OF CONVERTING MODES OF WAVE MOTION FOR TRANSMISSION FROM RECTANGULAR TO CIRCULAR WAVE GUIDES Filed Dec. 15, 1951 3 Sheets-Sheet 2 FTci i F'G. INII/EN TOR.

FRANK E. PARIS] Feb. '25, 1958 F. E. PARISl 2,325,031

METHOD OF CONVERTING MODES OF WAVE MOTION FOR TRANSMISSION FROM RECTANGULAR TO CIRCULAR WAVE GUIDES Filed Dec. 15, 1951 3 Sheets-Sheet 3 INVENTOR.

FRANK EPARISI F7 M United States Patent METHOD OF CONVERTING MODES OF WAVE MOTION FOR TRANSMISSION FROM RECTAN- GULAR TO CIRCULAR WAVE GUIDES Frank E. Parisi, Waban, Mass, assignor to Andrew Alford, Boston, Mass.

Application December 15, 1951, Serial No 261,882

4 Claims. (Cl. 333-21) The present invention relates to a method and means of creating certain modes of wave motion in circular wave guides and in particular relates to the creation of TE in circular wave guides. Notations here used are the same as in Electromagnetic Waves, by S. A. Sehelkunotf; published by Van Nostrand Co., lnc., 1943, p. 395. While energy is transmitted between wave guides which may be rotated relative to each other about a common axis, it is necessary to maintain circular symmetry in the wave guide, that is the electric and magnetic fields should be constant in magnitude and phase and in the same radial or tangential direction at any point of a circle whose center is on the axis of rotation and which is in a plane normal to this axis. This condition is needed to maintain constant power through the joint during rotation and constant impedance presented to the source. In order to accomplish this result, a tube having a circular symmetry, namely a cylindrical tube, should be used on which is impressed a wave having a mode of propagation which possesses this symmetry.

The present invention more particularly relates to the method and means for producing a wave which has such a mode. of propagation. The applicant has discovered that such a mode of propagation may be provided by using four rectangular wave guides arranged in a cross each equally excited in a TE mode and then having such wave guides connected to the cylindrical tubing in 2,825,031 Patented Feb. 25, 1958 Figure 7 shows in detail a further converting section which may be employed in the present invention, and,

Figure 8 shows an arrangement for rotating a directive element.

Referring to the diagrams of Figures and 6, more particularly to Figure 6, 1 shows a wave guide having a mode of propagation TE in which the arrows a, indicate the direction of the electric field. A central conductive partition 2 parallel to the long side of the guide 1 will not affect the field pattern, so that in effect the wave guide 1 is thereby split up into two wave guides 3 and 4 both having TE modes of vibration.

By curving the wave guide 4 to the position of the guide 5 and the wave guide 3 to the position of the wave guide 6 and joining these two guides as a single guide, a wave guide is produced which has a TE mode.

It will be noted that in such a wave guide the E vector in one half of the guide is in the opposite direction from that in the other half of the guide as indicated by the arrows b, b.

At the central plane of the guide 5, 6, a partition 7 may be inserted across the guide without affecting the directions of the electrical potentials, since in this median plane, the potential is zero. A lengthwise partition may also be inserted running centrally for the length of the guide also without disturbing the pattern, since the electric lines of force are perpendicular to this conductive partition. There are thereby formed, four individual wave guides, 9, 10, 11 and 12, each having a TE mode with one set 9 and 10 having the electric field running transversely of the guides in the same direction, but opsuch a way that the electric field is directed in the same tangential direction to concentric circles normal to the axis of the tube. If desired the walls of the rectangular guide may be tapered outward to makea gradual transition with the circular tube, but it will be found that good results are also obtained without such tapering sections.

The rectangular cross guide mentioned above with the electrical field arranged in the proper direction may be obtained from a wave guide having a TE mode andthis isprobably the simplest manner in which thecircular field of symmetry may be created.

The method and means of providing the desired mode of propagation will be morefully understood from a description in the specification set forth below when taken in connection with the drawings illustrating the same, in which:

Figure 1 shows in perspective a section of a wave guide. for converting a TE mode into one having axial symmetry.

Figure 2 shows a broken away view as viewed from the top of Figure 1.

Figure 3 shows a plan view of a section fittingfover the section of Figure 1.

Figure 4 shows a section takenon the line 4-4 of Figure 3.

Figure 5 shows diagrammatically the steps in going from the one mode of propagation. to the other.

Figure 6 shows diagrammatically an arrangement for establishing the modes shown in Figure 5, and,

posite to that of the electric field in the other pair of guides 11 and 12. By twisting each of these guides to a position where the long axis of each guide is 45 from its adjacent guide, the desired pattern having an approximate circular symmetry is obtained.

In the arrangement of Figure 6, the guide 10 has a 45 twist to bring it to a position 10'. This twist is in the direction of the arrow 0. The electric field as indicated by the arrow d will be tangential to circles in a normal plane about the axis of the circular guide whichis coincident with the center point 0. Similarly the guide 9 is twisted to a position9'. and the arrows e are also tangential to the same circle as the arrows d and'inthe same clockwise direction. The twist from 9 to 9" is in the direction of the arrow 1 and is 45. In similar. fashion the wave guides 11 and 12 are twisted to have their other ends in the position 11" and 12 respectively-,- and in this case the arrows g'and h are in the same clockwise directions as the arrows d and e. The positions of the ends of the four guides 9', 10', 11" and 12', have the figure of a cross which should preferably bel; at angles of from each other. The guides need maintain the same length and width dimensions through the twist.

As indicated in Figure 6, the end of the guide 5 is tapered to a larger widthdimension than that of the guide 4. Similarly the end of the guides 9' and be tapered to larger width dimensions than the ends 9" and 10. This tapering should be gradual and the laws relative to dimensions of the wave guide should be observed. For a TE modein rectangular wave guidesthe longest transverse dimension of the tube must be greater than X/Z where X is'the longest wave lengthof the band to be transmitted, but this dimension preferably should not be greater than for if that" occurs it is possible to excite the TE mode of vibration which is that shown in. the vertical wave guide of Figure" 6, namely the combination of the two guides 5 and 6;

While the wave guides in Figure 6il1'a've' be'en'shown as rectangular inshape, this exact-shape of guide need ,2 arrangement the waveguide 2 is made. to pass .sucha of the axis "of the guide. fWhere a TM mode is used,

suitable'screws 46, but it is not necessarythat conductive contact-needbe maintained although there is no objection not be maintained and transitional'gradual changes may 7 be *madeand different forms may be used asflong as the same mode of wave propagation is maintained; In t h s V 7 thejransition fronr the rectangular cross guide to the The "section 43 is interconnectedat its lower; corners. circular guide, 'the side"wal lsof"therectanglesmaybe by suitable means to adjacent lower portions. of the tapered gradually toin c rease the "guide opening to the y casing forming theopenings 36, 37, 38 and-39. f 'j y cylindrical form as will be more fully described in con-" In the arrangement indicated in-Figure 7, the guides 3 nection with'the drawings of Figures 3 2116.4. j 7 V emerging in T S as i d c te in gureqlg'aref rtheri The arrangement shown in Figure 5 shows the transi: divided 'asl indicatedlin.theupper section of the figure, V .tion of a wave guide was TE i mode to a cross rec- .Here the guideend 37 'I PQ fi m al tangnlar; mode. for presenting a circular field. 'In this 7 in Figure J SR K by a Q lip I ifi l going lengthwise f of the guide'andtormediinto two'separateguides.60and j 1 y 61, emerging fro'mjth e retaining' plate or fiange621which f i is normally joined inlface t'o face contact witlif the3plate 40 of thelower section .showniin Figure 7. 'Similarlyz each .of the eiids"3l6, 38 'ia nd 39'-oftlrefwave guides .are, V split'to form separateguides 63,64-forthe guide36;"65,' y 66 for the guide 38, and 67; 68 for the'guide Ihese split guides form a.regular'jsymmetrical 'p'a'ttern-iof'ight guides each radially spacedin' their longitudinalfaxes of 45 forming'acenter octagonal polygon opening as indi-f. cated at 69' in the top dise or flange; 7.9 m which the f guides are secured. I The fields emerging from'theseguides I i have their'electrical components all. rotated inthesame direction forming a substantially circular rotation patternf 'r'node by'rnaking the transverse long dimension of the i guidegreat er than the wave length k where .X'is defined as above set forth. j I11 this case the partitions 21' and 22 may; be inserted in thefguide cross-wise as. indicated without disturbing the wave form of the guide as'a whole, but it will beob's'erved that such partitions convert the guide into four wave guides;-each with a Tli mode as .describedinfFigure 6. Itzis only; necessary therefore to produce the rectangular cross guide having the proper: wave motion to rotate'the individual guides to 45 posit tions asindicated by the dotted line elements 23, 24, :25 and -26. It will be noted that the directions of the' arrows denoting the E vectors are in'the same direction 7 Tot rotation, namely, clockwise. In this case the mag netic' field'is in 'a radial direction with respect to the axis of the guideand'the propagationisin' the direction ofaTE mode of propagation, V y The 'waveemerging from the upper section ofFigure' 7;

is more preferable than." thatemergin'g'v from fthellowe'r' 1 1 section because adjacent electric components are 'now f at an angle of '45 "1 as they.'emerge from the. wavegguide rather than at an 'angle'of 90 as is the casein theilower section of Figure 7; y This provides a considerable imj provement in the propagational mode;enteringthecircu lar wave guide and smoothsrout the form of suchlan' extent that a substahtiallycircular pattern-is obtained.. 5

In the arrangement'indicated inFigure 8,"there is shown a means by which directionaljrotation of a radiant' source may be obtained by means of fthe pre'sent f q the magnetic and electrical lines are interchanged with the same resulting type of propagation. The actual'form of structure 'producing the propagation modes as set-forth in Figures 5 and 6 is shown-in Figures 1 and 2.

Referringmorespecifically to these figures, 30 is a X f flange plate which has an-opening in its bottom. face, not

. shown; in which a wave guide 31 is secured. ;This wa ve guide 31 is of'theform shown in Figureja't 20; with the TE mode. The waveguide is provided-With two' right angled partitions which divides'the guide into four .lllvemlolh' 7 I a a sections, '32, 33.34 and 3s.. At'the back of thefplate -Referringamoreipartiwlarly u M waveguide ii 30, these sections emerge asindividual wave guides-each 71 ay h S 't T- input m c u' i 1 i 7 having a'propagating mode corresponding respectively to the individual guides of. Figure 5,' namely, sections 23,, Y 24, ZS fand 26. The guides 32,. 33; '34a'nd 35, are

twisted'orspiralle'd gradually over a section which prefer-f ably shouldbe substantiallytwo wave lengths-within the as far asthe mode of propagation is concerned, is con-' .nected with an; element 72 corresponding'to the' elernent; shown in' F igure l which convertsthe'wave --motion from l V the rectangular guide .to'a circular guide 73. which. forms a continuation of the conversion'section72. 'The'section' j frequency range propagated to produceat the output end, I V Y PQ 1 vvt0 h n' a '1 W l V across 'form as indicated by' the openings 36,37, 38 and be aic mbi a f the two im s h niFig el" I 39. These ends36, 37, 38 and 39, corresponding to the i The cil'culalrwagve guide 73i$hQ111d P i 'P T Y"d -f V 7 guides 32;"33,34 and 35, may terminatein' conductive SiOIIedISO thatiit'will P888 thed sired frequency/{namely}.

f flang'e plate 40 over which the section42, Figures 3"and. the diameter Q i h g de should su s i y bc 'equalfl V 4, may be 'placedexpanding] the cross openings :to a. @101 n1- 2 h eN SK WaYQ f! cylindricalwave guide. This combination willprodiice. h c f q n w Ihe-drcuhrsectidn n w e the necessary circular symmetry so that atu'bezmay" be rotating Section 74 m n 01110? I I mountedfor rotation'about'its. axis :to produce a radia-L Figure sfsh'ows'ia'collvellfiolial'dfive i ld 'fl tion which may be rotated around its wholej.,360 ,asi a Worm gear-76 a d a I l' mpunted Q indicated md e specifically in Fig u e 8 7 y the outside .Of thfi l'btatll'lg .74; The;- 7 Any of the standard means usually. employed for ro- Y Q d 7 1% be pl d 'wii gwb g a I f tating antennas may be. us'edfsuch for instance as .a'horn' Which is pp r d niball, bearing races .79he1d in V or a reflecting element or a directive array orjloop. f :P y fl L il .securediiolithiii- V Ihe' invention in the pres'ent;'ca'se is more particularly flange of the Y1indrical g i; j a concerned with the production of the'desired propagah t a fi ciisu r l r v e'convcrt: I 7 5 1 1 mod I g y 7 ,ing element 82'iis placed which willjconvertthe circular '';-'It:has,beenfoundpthat thejrectangular cross as prod I fromthe" cylindfl 74 eventually 1 r 7 id i Fi 51 may haverits input into a mode suitable for the rectangular guide 83 from which circular waveguideand there -isno necessity thatlthe. I the f may be convfiyeddo med at n h rn Q l' 7 two guides-be conductively connected together.: r other radiating i l h la a flector or other unit.

The section shown in Figures .3 and 4 may be mounted V on top of the flange 40. In. this case .the openingsas.

for instance 36 and '38 may be expanded with gradually expanding, central'and' outward sections 43 and 44.1fespectivelyin smooth continuous surfaces toithe inner wall 45 of thecylindn'cal. tubing. Each one of the four rectangular 'openingsshould ;befex'panded in the same way, ';Ihe section ,42 may. be held toQ the flange 40. by

It will be evident fromath'efarrangementin Figure 8 that the 'horn may. be. rotated [aroundeompleterggtr without disturbingthewave propagation in .the;system.

The arrangement which has been described in 'co'nnection'w'ith Figure8 is'only one" of the many'forrn's to V which the conversion and reconversion from rectangular guidesjtocircular; ori'cylindrical' guides are usefully; v

applied.

Wherever it is desired to rotate a section of the wave guide with respect to another section of the wave guide, this cannot be efficiently accomplished except by means as generally set forth in the present invention.

Having now described my invention, I claim:

1. An apparatus for producing a TE mode of propagation in a circular wave guide comprising two sections, said first section having four rectangular wave guides, each having propagational modes of TE having gradual spiral twists into positions forming a pattern of a uniform cross with a square center formed of the short sides of the wave guides, said second section fitting to said first section and having a central conductive core element fitting over said square and tapering to a point in axial alignment with the center of symmetry of said pattern and wall elements tapering outwardly from the sides or" the rectangular wave guides to diagonal planes coinciding with the diagonals of said square and from the outer ends and sides of the rectangular guides to cylindrical walls coaxial with said center of symmetry and said cylindrical wall elements.

2. An apparatus for producing a TE mode of propagation in a circular wave guide, comprising two sections, said first section having four rectangular wave guides, each having propagational modes of TE having gradual spiral twists into positions forming a pattern of a uniform cross with a square center formed of the short sides of the rectangular wave guides, a second section having a central conductive core element fitting over said square center and tapering to a point in axial alignment with the center of symmetry of said cross pattern, and having a cylindrical wall at one end and having at its other end surrounding said core, a pattern fitting said uniform cross pattern, conductive means extending inwardly in said second section from the end having said uniform cross providing conductive members tapering to diagonal planes coinciding with the diagonals of said cross and other conductive wall elements tapering outward to said cylindrical wall.

3. An apparatus for producing a TE mode of propagation in a circular wave guide comprising four rectangular wave guides, each having progational modes of TE said wave guides forming a section with four guides twisted from a rectangular position into a cross pattern, each said guide in said rectangular position being symmetrical about a center axis and equally spaced therefrom with the electric vectors having the same angular direction of rotation, at second wave guide section mounted on the cross pattern end of said first section, said second section having cylindrical conductive walls with a center conductive section tapering to a point co axial with the cylinder from the inner adjacent sides of the f ur rectangular guides and with partitioning sections formed with sides of the guides at right angles to each other tapering to diagonal lines across the'cylinder.

4. An apparatus for producing a TE mode of propagation in a circular waveguide comprising two sections, said first section having an even numbered plurality of at least four rectangular waveguides, each having propagational modes of TE having gradual spiral twists into positions forming a uniform equiangular pattern with a regular polygon center formed of the short sides of the waveguides, said second section fitting to said first section and having a central conductive core element fitting over said polygon and tapering to a point in axial alignment with the center of symmetry of said pattern and wall elements tapering outwardly from the sides of the rectangular waveguides to diagonal planes coinciding with the diagonals of said polygon and from the outer ends and sides of the rectangular guides to cylindrical walls coaxial with said center of symmetry and said cylindrical wall elements.

References Cited in the file of this patent UNITED STATES PATENTS 2,439,285 Clapp Apr. 6, 1948 2,455,158 Bradley Nov. 30, 1948 2,534,876 Ortusi Dec. 19, 1950 2,543,188 Moseley Feb. 27, 1951 2,584,399 Preston Feb. 5, 1952 

